A sham stimulation-controlled trial of rTMS of the unaffected hemisphere in stroke patients

Non-invasive brain stimulation in neurorehabilitation: local and distant effects for motor recovery

Non-invasive brain stimulation (NIBS) may enhance motor recovery after neurological injury through the causal induction of plasticity processes. Neurological injury, such as stroke, often results in serious long-term physical disabilities, and despite intensive therapy, a large majority of brain injury survivors fail to regain full motor function. Emerging research suggests that NIBS techniques, such as transcranial magnetic (TMS) and direct current (tDCS) stimulation, in association with customarily used neurorehabilitative treatments, may enhance motor recovery. This paper provides a general review on TMS and tDCS paradigms, the mechanisms by which they operate and the stimulation techniques used in neurorehabilitation, specifically stroke. TMS and tDCS influence regional neural activity underlying the stimulation location and also distant interconnected network activity throughout the brain. We discuss recent studies that document NIBS effects on global brain activity measured with various neuroimaging techniques, which help to characterize better strategies for more accurate NIBS stimulation. These rapidly growing areas of inquiry may hold potential for improving the effectiveness of NIBS-based interventions for clinical rehabilitation.

Broca's area damage is necessary but not sufficient to induce after-effects of cathodal tDCS on the unaffected hemisphere in post-stroke aphasia

BACKGROUND

The inter-individual variability of behavioral effects after tDCS applied to the unaffected right hemisphere in stroke may be related to factors such as the lesion location.

OBJECTIVE/HYPOTHESIS

We investigated the effect of left Broca's area (BA) damage on picture naming in aphasic patients after cathodal tDCS applied over the right BA.

METHODS

We conducted a study using pre-interventional diffusion and resting state functional MRI (rsfMRI) and two cross-over tDCS sessions (TYPE: sham and cathodal) over the right homologous BA in aphasic stroke patients with ischemic lesions involving the left BA (BA+) or other left brain areas (BA-). Picture naming accuracy was assessed after each session. Inter-hemispheric (IH) functional balance was investigated via rsfMRI connectivity maps using the right BA as a seed. Probabilistic tractography was used to study the integrity of language white matter pathways.

RESULTS

tDCS had different effects on picture naming accuracy in BA+ and BA- patients (TYPE × GROUP interaction, F(1,19): 4.6, P: 0.04). All BA- patients except one did not respond to tDCS and demonstrated normal IH balance between the right and left BA when compared to healthy subjects. BA+ patients were improved by tDCS in 36% and had decreased level of functional IH balance. Improvement in picture naming after cathodal tDCS was associated with the integrity of the arcuate fasciculus in BA+ patients.

CONCLUSIONS

Behavioral effects of cathodal tDCS on the unaffected right hemisphere differ depending on whether BA and the arcuate fasciculus are damaged. Therefore, IH imbalance could be a direct consequence of anatomical lesions.

Evidence-based guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS)

A group of European experts was commissioned to establish guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS) from evidence published up until March 2014, regarding pain, movement disorders, stroke, amyotrophic lateral sclerosis, multiple sclerosis, epilepsy, consciousness disorders, tinnitus, depression, anxiety disorders, obsessive-compulsive disorder, schizophrenia, craving/addiction, and conversion. Despite unavoidable inhomogeneities, there is a sufficient body of evidence to accept with level A (definite efficacy) the analgesic effect of high-frequency (HF) rTMS of the primary motor cortex (M1) contralateral to the pain and the antidepressant effect of HF-rTMS of the left dorsolateral prefrontal cortex (DLPFC). A Level B recommendation (probable efficacy) is proposed for the antidepressant effect of low-frequency (LF) rTMS of the right DLPFC, HF-rTMS of the left DLPFC for the negative symptoms of schizophrenia, and LF-rTMS of contralesional M1 in chronic motor stroke. The effects of rTMS in a number of indications reach level C (possible efficacy), including LF-rTMS of the left temporoparietal cortex in tinnitus and auditory hallucinations. It remains to determine how to optimize rTMS protocols and techniques to give them relevance in routine clinical practice. In addition, professionals carrying out rTMS protocols should undergo rigorous training to ensure the quality of the technical realization, guarantee the proper care of patients, and maximize the chances of success. Under these conditions, the therapeutic use of rTMS should be able to develop in the coming years.

Patterns of structural reorganization of the corticospinal tract in children with Sturge-Weber syndrome

BACKGROUND

Reorganization of the corticospinal tract after early damage can limit motor deficit. In this study, we explored patterns of structural corticospinal tract reorganization in children with Sturge-Weber syndrome.

METHODS

Five children (age 1.5-7 years) with motor deficit resulting from unilateral Sturge-Weber syndrome were studied prospectively and longitudinally (1-2 years follow-up). Corticospinal tract segments belonging to hand and leg movements were separated and their volume was measured by diffusion tensor imaging tractography using a recently validated method. Corticospinal tract segmental volumes were normalized and compared between the Sturge-Weber syndrome children and age-matched healthy controls. Volume changes during follow-up were also compared with clinical motor symptoms.

RESULTS

In the Sturge-Weber syndrome children, hand-related (but not leg-related) corticospinal tract volumes were consistently decreased in the affected cerebral hemisphere at baseline. At follow-up, two distinct patterns of hand corticospinal tract volume changes emerged. (1) Two children with extensive frontal lobe damage showed a corticospinal tract volume decrease in the lesional hemisphere and a concomitant increase in the nonlesional (contralateral) hemisphere. These children developed good hand grasp but no fine motor skills. (2) The three other children, with relative sparing of the frontal lobe, showed an interval increase of the normalized hand corticospinal tract volume in the affected hemisphere; these children showed no gross motor deficit at follow-up.

CONCLUSIONS

Diffusion tensor imaging tractography can detect differential abnormalities in the hand corticospinal tract segment both ipsi- and contralateral to the lesion. Interval increase in the corticospinal tract hand segment suggests structural reorganization, whose pattern may determine clinical motor outcome and could guide strategies for early motor intervention.

Effects of repetitive transcranial magnetic stimulation and intensive occupational therapy on motor neuron excitability in poststroke hemiparetic patients: a neurophysiological investigation using F-wave parameters

BACKGROUND

The combination protocol of repetitive transcranial magnetic stimulation (RTMS) and intensive occupational therapy (OT) improves motor function of the paretic upper limb in poststroke patients. However, the effect of RTMS/OT on motor neuron excitability remains to be investigated. The purpose of this study was to determine the effect of 15-day application of RTMS/OT on motor neuron excitability in such patients using neurophysiological studies including F-wave parameter measurements.

SUBJECTS AND METHODS

Ten poststroke patients with spastic upper limb hemiparesis were studied (mean age: 57.4 ± 8.1 years, ± SD). Patients were hospitalized for 15 days to receive RTMS/OT. One session of 40-min low-frequency RTMS and two sessions of 120-min intensive OT were provided daily. Neurophysiological studies including F-wave parameters measurements were performed on the days of admission/discharge. Motor function and spasticity of the affected upper limb were evaluated on the same time points.

RESULTS

RTMS/OT significantly improved motor function of the affected upper limb. RTMS/OT decreased the modified Ashworth scale (MAS) in the affected upper limb (p < 0.05), but did not change F-wave frequency in either upper limb. However, both F-mean/M ratio and F-max/M ratio significantly decreased in the affected upper limb (all p < 0.05).

CONCLUSIONS

The 15-day protocol of LF-RTMS/OT produced significant reduction of motor neuron excitability. RTMS/OT can potentially produce significant reduction in upper limb spasticity in the affected upper limb, although this finding should be confirmed in a larger number of patients.

Differential effect of conditioning sequences in coupling inhibitory/facilitatory repetitive transcranial magnetic stimulation for poststroke motor recovery

INTRODUCTION

While neuromodulation through unihemispheric repetitive transcranial magnetic stimulation (rTMS) has shown promise for the motor recovery of stroke patients, the effectiveness of the coupling of different rTMS protocols remains unclear.

AIMS

We aimed to test the long-term efficacy of this strategy with different applying sequences and to identify the electrophysiological correlates of motor improvements to the paretic hand.

RESULTS

In our sham-controlled, double-blinded parallel study, 48 stroke patients (2-6 months poststroke) were randomly allocated to three groups. Group A underwent 20-session rTMS conditioning initiated with 10-session 1 Hz rTMS over the contralesional primary motor cortex (M1), followed by 10-session intermittent theta burst stimulation (iTBS) consequently over the ipsilesional M1; Group B underwent the same two paradigms but in reverse; and Group C received sham stimulation that was identical to Group A. We tested cortical excitability and motor assessments at the baseline, postpriming rTMS, postconsequent rTMS, and at 3-months follow-up. Group A manifested greater improvement than Group B in Fugl-Meyer Assessment (FMA), Wolf Motor Function testing (WMFT) score, and muscle strength (P = 0.001-0.02) post the priming rTMS. After the consequent rTMS, Group A continued to present a superior outcome than Group B in FMA (P = 0.015) and WMFT score (P = 0.008) with significant behavior-electrophysiological correlation.

CONCLUSIONS

Conditioning the contralesional M1 prior to ipsilesional iTBS was found to be optimal for enhancing hand function, and this effect persisted for at least 3 months. Early modulation within 6 months poststroke rebalances interhemispheric competition and appears to be a feasible time window for rTMS intervention.

Use of transcranial magnetic stimulation of the brain in stroke rehabilitation

Preliminary studies suggest that stimulation of the motor cortex enhances motor recovery after stroke. Most of these studies employed transcranial magnetic stimulation of the brain and two different approaches have been evaluated. The first approach is based on the use of protocols of stimulation that increase cortical excitability, targeting the hemisphere in which the stroke occurred in order to enhance the output of the motor cortex and the response to physiotherapy. The second approach is based on the use of protocols of stimulation that suppress cortical excitability, targeting the intact hemisphere in order to counteract the imbalance due to the increased interhemispheric inhibition onto the lesioned cortex, and reducing the potential negative interference of the intact hemisphere with the function of the affected one. Cumulatively, preliminary studies suggest that transcranial magnetic stimulation might be a suitable method to combine with physiotherapy and improve recovery of useful limb function in stroke patients. However, further studies are needed to determine the best stimulation parameters and how to select patients who are likely to respond to this treatment.

Contribution of the resting-state functional connectivity of the contralesional primary sensorimotor cortex to motor recovery after subcortical stroke

It remains uncertain if the contralesional primary sensorimotor cortex (CL_PSMC) contributes to motor recovery after stroke. Here we investigated longitudinal changes in the resting-state functional connectivity (rsFC) of the CL_PSMC and their association with motor recovery. Thirteen patients who had experienced subcortical stroke underwent a series of resting-state fMRI and clinical assessments over a period of 1 year at 5 time points, i.e., within the first week, at 2 weeks, 1 month, 3 months, and 1 year after stroke onset. Thirteen age- and gender-matched healthy subjects were recruited as controls. The CL_PSMC was defined as a region centered at the voxel that had greatest activation during hand motion task. The dynamic changes in the rsFCs of the CL_PSMC within the whole brain were evaluated and correlated with the Motricity Index (MI) scores. Compared with healthy controls, the rsFCs of the CL_PSMC with the bilateral PSMC were initially decreased, then gradually increased, and finally restored to the normal level 1 year later. Moreover, the dynamic change in the inter-hemispheric rsFC between the bilateral PSMC in these patients was positively correlated with the MI scores. However, the intra-hemispheric rsFC of the CL_PSMC was not correlated with the MI scores. This study shows dynamic changes in the rsFCs of the CL_PSMC after stroke and suggests that the increased inter-hemispheric rsFC between the bilateral PSMC may facilitate motor recovery in stroke patients. However, generalization of our findings is limited by the small sample size of our study and needs to be confirmed.

Effects of the motor cortical quadripulse transcranial magnetic stimulation (QPS) on the contralateral motor cortex and interhemispheric interactions

Corpus callosum connects the bilateral primary motor cortices (M1s) and plays an important role in motor control. Using the paired-pulse transcranial magnetic stimulation (TMS) paradigm, we can measure interhemispheric inhibition (IHI) and interhemispheric facilitation (IHF) as indexes of the interhemispheric interactions in humans. We investigated how quadripulse transcranial magnetic stimulation (QPS), one form of repetitive TMS (rTMS), on M1 affects the contralateral M1 and the interhemispheric interactions. QPS is able to induce bidirectional plastic changes in M1 depending on the interstimulus intervals (ISIs) of TMS pulses: long-term potentiation (LTP)-like effect by QPS-5 protocol, and long-term depression-like effect by QPS-50, whose numbers indicate the ISI (ms). Twelve healthy subjects were enrolled. We applied QPS over the left M1 and recorded several parameters before and 30 min after QPS. QPS-5, which increased motor-evoked potentials (MEPs) induced by left M1 activation, also increased MEPs induced by right M1 activation. Meanwhile, QPS-50, which decreased MEPs elicited by left M1 activation, did not induce any significant changes in MEPs elicited by right M1 activation. None of the resting motor threshold, active motor threshold, short-interval intracortical inhibition, long-interval intracortical inhibition, intracortical facilitation, and short-interval intracortical inhibition in right M1 were affected by QPS. IHI and IHF from left to right M1 significantly increased after left M1 QPS-5. The degree of left first dorsal interosseous MEP amplitude change by QPS-5 significantly correlated with the degree of IHF change. We suppose that the LTP-like effect on the contralateral M1 may be produced by some interhemispheric interactions through the corpus callosum.

Behavioral and neuroplastic effects of low-frequency rTMS of the unaffected hemisphere in a chronic stroke patient: a concomitant TMS and fMRI study

Repetitive Transcranial Magnetic Stimulation (rTMS) ameliorates motor and neuropsychological deficits following stroke, but little is known about the underlying neuroplasticity. We investigated neuroplastic changes following 5 days of low-frequency rTMS on the intact motor cortex to promote motor recovery in a chronic patient with subcortical stroke. The feasibility of administering multiple treatments was also assessed 6 months later by applying the same protocol over the patient's parietal cortex to improve visuospatial disorders. Behavioral improvements and no adverse events were observed. Neuroimaging findings indicated that motor symptoms amelioration was associated with downregulation and cortical reorganization of hyperactive contralesional hemisphere.

Studying the effects of transcranial direct-current stimulation in stroke recovery using magnetic resonance imaging

Transcranial direct-current stimulation (tDCS) is showing increasing promise as an adjunct therapy in stroke rehabilitation. However questions still remain concerning its mechanisms of action, which currently limit its potential. Magnetic resonance (MR) techniques are increasingly being applied to understand the neural effects of tDCS. Here, we review the MR evidence supporting the use of tDCS to aid recovery after stroke and discuss the important open questions that remain.

Combining rTMS and Task-Oriented Training in the Rehabilitation of the Arm after Stroke: A Pilot Randomized Controlled Trial

Introduction. Repetitive transcranial magnetic stimulation (rTMS) is a promising technique for promoting rehabilitation of arm function after stroke. The feasibility and impact of rTMS as an adjunct to traditional task-oriented training to improve arm function have not yet been demonstrated. Objective. Evaluate the feasibility of a randomized controlled trial aimed at determining the efficacy of rTMS as an adjunct to task-oriented therapy in facilitating restoration of arm function after stroke. Methods. Stratified block-randomized controlled trial set in the general community. Eleven stroke persons with mild to severe arm deficits were recruited and randomized to receive 8 sessions of real-rTMS or sham-rTMS followed by ninety minutes of arm tasks designed to improve function. Results. Medium to large, statistically significant effect sizes (0.49 to 1.63) were observed in both groups on several measures of arm function at the postintervention evaluation. Three out of four subjects in the real-TMS condition showed increased levels of corticomotor excitability after the first stimulation session. Conclusions. Preliminary evidence suggests that an rTMS protocol potent enough to induce transient increases in cortical excitability of the lesioned hemisphere is feasible but did not show promising results as an adjunct to task-specific training. This trial is registration with Clinical Trials.gov NCT00850408.

Applications of transcranial magnetic stimulation and magnetic seizure therapy in the study and treatment of disorders related to cerebral aging

Transcranial magnetic stimulation (TMS) can be used to probe cortical function and treat neuropsychiatric illnesses. TMS has demonstrated neuroplastic effects akin to long-term potentiation and long-term depression, and therapeutic applications are in development for post-stroke recovery, Alzheimer's disease, and depression in seniors. Here, we discuss two new directions of TMS research relevant to cerebral aging and cognition. First, we introduce a paradigm for enhancing cognitive reserve, based on our research in sleep deprivation. Second, we discuss the use of magnetic seizure therapy (MST) to spare cognitive functions relative to conventional electroconvulsive therapy, and as a means of providing a more potent antidepressant treatment when subconvulsive TMS has shown modest efficacy in seniors. Whether in the enhancement of cognition as a treatment goal, or in the reduction of amnesia as a side effect, these approaches to the use of TMS and MST merit further exploration regarding their clinical potential.

High-frequency rTMS using a double cone coil for gait disturbance

OBJECTIVE

It is difficult to stimulate leg motor areas with magnetic current using a figure-of-eight coil due to the deep anatomical location of the areas. However, a double cone coil is useful for stimulating deep brain regions. We postulated that the use of the same coil may allow repetitive transcranial magnetic stimulation (rTMS) to modulate the neural activity of the same areas. The purpose of this study is to investigate the effect of high-frequency rTMS applied over bilateral leg motor areas with a double cone coil on walking function after stroke.

MATERIALS AND METHODS

Eighteen post-stroke hemiparetic patients with gait disturbances attended two experimental sessions with more than 24 h apart, in a cross-over, double-blind paradigm. In one session, high-frequency rTMS of 10 Hz was applied over the leg motor area bilaterally in a 10-s train using a double cone coil for 20 min (total 2,000 pulses). In the other session, sham stimulation was applied for 20 min at the same site. To assess walking function, walking velocity, and Physiological Cost Index (PCI) were evaluated serially before, immediately after, and 10 and 20 min after each stimulation.

RESULTS

The walking velocity was significantly higher for 20 min after stimulation in the high-frequency rTMS group than the sham group. PCI was lower in the high-frequency rTMS group than the sham group, but this was significant only immediately after stimulation.

CONCLUSIONS

High-frequency rTMS of bilateral leg motor areas using a double cone coil can potentially improve walking function in post-stroke hemiparetic patients.

Short- and long-latency interhemispheric inhibitions are additive in human motor cortex

Transcranial magnetic stimulation (TMS) of the human primary motor cortex (M1) at suprathreshold strength results in inhibition of M1 in the opposite hemisphere, a process termed interhemispheric inhibition (IHI). Two phases of IHI, termed short-latency interhemispheric inhibition (SIHI) and long-latency interhemispheric inhibition (LIHI), involving separate neural circuits, have been identified. In this study we evaluated how these two inhibitory processes interact with each other. We studied 10 healthy right-handed subjects. A test stimulus (TS) was delivered to the left M1, and motor evoked potentials (MEPs) were recorded from the right first dorsal interosseous (FDI) muscle. Contralateral conditioning stimuli (CCS) were applied to the right M1 either 10 ms or 50 ms prior to the TS, inducing SIHI and LIHI, respectively, in the left M1. The effects of SIHI and LIHI alone, and SIHI and LIHI delivered together, were compared. The TS was adjusted to produce 1-mV or 0.5-mV MEPs when applied alone or after CCS. SIHI and LIHI were found to be additive when delivered together, irrespective of the strength of the TS. The interactions were affected neither by varying the strength of the conditioning stimulus producing SIHI nor by altering the current direction of the TS. Small or opposing interactions, however, may not have been detected. These results support previous findings suggesting that SIHI and LIHI act through different neural circuits. Such inhibitory processes may be used individually or additively during motor tasks and should be studied as separate processes in functional studies.

Enhancement of human cognitive performance using transcranial magnetic stimulation (TMS)

Here we review the usefulness of transcranial magnetic stimulation (TMS) in modulating cortical networks in ways that might produce performance enhancements in healthy human subjects. To date over sixty studies have reported significant improvements in speed and accuracy in a variety of tasks involving perceptual, motor, and executive processing. Two basic categories of enhancement mechanisms are suggested by this literature: direct modulation of a cortical region or network that leads to more efficient processing, and addition-by-subtraction, which is disruption of processing which competes or distracts from task performance. Potential applications of TMS cognitive enhancement, including research into cortical function, rehabilitation therapy in neurological and psychiatric illness, and accelerated skill acquisition in healthy individuals are discussed, as are methods of optimizing the magnitude and duration of TMS-induced performance enhancement, such as improvement of targeting through further integration of brain imaging with TMS. One technique, combining multiple sessions of TMS with concurrent TMS/task performance to induce Hebbian-like learning, appears to be promising for prolonging enhancement effects. While further refinements in the application of TMS to cognitive enhancement can still be made, and questions remain regarding the mechanisms underlying the observed effects, this appears to be a fruitful area of investigation that may shed light on the basic mechanisms of cognitive function and their therapeutic modulation.

Je pense donc je fais: transcranial direct current stimulation modulates brain oscillations associated with motor imagery and movement observation

Motor system neural networks are activated during movement imagery, observation and execution, with a neural signature characterized by suppression of the Mu rhythm. In order to investigate the origin of this neurophysiological marker, we tested whether transcranial direct current stimulation (tDCS) modifies Mu rhythm oscillations during tasks involving observation and imagery of biological and non-biological movements. We applied tDCS (anodal, cathodal, and sham) in 21 male participants (mean age 23.8 ± 3.06), over the left M1 with a current of 2 mA for 20 min. Following this, we recorded the EEG at C3, C4, and Cz and surrounding C3 and C4 electrodes. Analyses of C3 and C4 showed significant effects for biological vs. non-biological movement (p = 0.005), and differential hemisphere effects according to the type of stimulation (p = 0.04) and type of movement (p = 0.02). Analyses of surrounding electrodes revealed significant interaction effects considering type of stimulation and imagery or observation of biological or non-biological movement (p = 0.03). The main findings of this study were (1) Mu desynchronization during biological movement of the hand region in the contralateral hemisphere after sham tDCS; (2) polarity-dependent modulation effects of tDCS on the Mu rhythm, i.e., anodal tDCS led to Mu synchronization while cathodal tDCS led to Mu desynchronization during movement observation and imagery (3) specific focal and opposite inter-hemispheric effects, i.e., contrary effects for the surrounding electrodes during imagery condition and also for inter-hemispheric electrodes (C3 vs. C4). These findings provide insights into the cortical oscillations during movement observation and imagery. Furthermore, it shows that tDCS can be highly focal when guided by a behavioral task.

Can noninvasive brain stimulation measure and modulate developmental plasticity to improve function in stroke-induced cerebral palsy?

The permanent nature of motor deficits is a consistent cornerstone of cerebral palsy definitions. Such pessimism is disheartening to children, families, and researchers alike and may no longer be appropriate for it ignores the fantastic plastic potential of the developing brain. Perinatal stroke is presented as the ideal human model of developmental neuroplasticity following distinct, well-defined, focal perinatal brain injury. Elegant animal models are merging with human applied technology methods, including noninvasive brain stimulation for increasingly sophisticated models of plastic motor development following perinatal stroke. In this article, how potential central therapeutic targets are identified and potentially modulated to enhance motor function within these models is discussed. Also, future directions and emerging clinical trials are reviewed.

Repetitive transcranial magnetic stimulation for improving function after stroke

BACKGROUND

It had been assumed that suppressing the undamaged contralesional motor cortex by repetitive low-frequency transcranial magnetic stimulation (rTMS) or increasing the excitability of the damaged hemisphere cortex by high-frequency rTMS will promote function recovery after stroke.

OBJECTIVES

To assess the efficacy and safety of rTMS for improving function in people with stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (April 2012), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 4), the Chinese Stroke Trials Register (April 2012), MEDLINE (1950 to May 2012), EMBASE (1980 to May 2012), Science Citation Index (1981 to April 2012), Conference Proceedings Citation Index-Science (1990 to April 2012), CINAHL (1982 to May 2012), AMED (1985 to May 2012), PEDro (April 2012), REHABDATA (April 2012) and CIRRIE Database of International Rehabilitation Research (April 2012). In addition, we searched five Chinese databases, ongoing trials registers and relevant reference lists.

SELECTION CRITERIA

We included randomised controlled trials comparing rTMS therapy with sham therapy or no therapy. We excluded trials that reported only laboratory parameters.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, assessed trial quality and extracted the data. We resolved disagreements by discussion.

MAIN RESULTS

We included 19 trials involving a total of 588 participants in this review. Two heterogenous trials with a total of 183 participants showed that rTMS treatment was not associated with a significant increase in the Barthel Index score (mean difference (MD) 15.92, 95% CI -2.11 to 33.95). Four trials with a total of 73 participants were not found to have a statistically significant effect on motor function (standardised mean difference (SMD) 0.51, 95% CI -0.99 to 2.01). Subgroup analyses of different stimulation frequencies or duration of illness also showed no significant difference. Few mild adverse events were observed in the rTMS groups, with the most common events being transient or mild headaches (2.4%, 8/327) and local discomfort at the site of the stimulation.

AUTHORS' CONCLUSIONS

Current evidence does not support the routine use of rTMS for the treatment of stroke. Further trials with larger sample sizes are needed to determine a suitable rTMS protocol and the long-term functional outcome.

A longitudinal study of hand motor recovery after sub-acute stroke: a study combined FMRI with diffusion tensor imaging

Previous studies have shown that motor recovery of stroke can be assessed by the cortical activity and the structural integrity of the corticospinal tract (CST), but little is known about the relation between the cortical activity and the structural integrity during motor recovery. In the present study, we investigated the changes in brain activities evoked by twenty days’ functional electrical stimulation (FES) training in twelve sub-acute stroke patients with unilateral upper-limb disability. We compared cortex activity evoked by wrist movement of eleven stroke patients to that of eleven age-matched healthy subjects to figure out how cortex activity changed after stroke. We also measured the structural integrity represented by the fractional anisotropy (FA) asymmetry of the posterior limb of the internal capsule (PLIC) to find the relationship between the brain activity and the structure integrity. In our study, we found that patients with sub-acute stroke have shown greater activity in the contralesional primary motor cortex (M1) during the affected hand’s movement compared with healthy group, while the activity in ipsilesional M1 was decreased after the therapy compared to that before therapy, and the contralesional non-primary motor cortex showed greater activity after therapy. At the baseline we found that the positive correlation between the FA asymmetry of PLIC and the contralesional non-primary motor cortex activity showed that the greater damaged CST, the greater contralesional non-primary motor cortex recruited. While the negative correlation between them after the FES training indicates that after recovery the non-primary motor cortex plays different role in different stroke phases. Our study demonstrates that functional organization of a residual distributed motor system is related to the degree of disruption to the CST, and the non-primary motor areas plays an important role in motor recovery.

Functional cortical reorganization after low-frequency repetitive transcranial magnetic stimulation plus intensive occupational therapy for upper limb hemiparesis: evaluation by functional magnetic resonance imaging in poststroke patients

BACKGROUND

Low-frequency repetitive transcranial magnetic stimulation of the nonlesional hemisphere combined with occupational therapy significantly improves motor function of the affected upper limb in poststroke hemiparetic patients, but the recovery mechanism remains unclear.

AIMS

To investigate the recovery mechanism using functional magnetic resonance imaging.

METHODS

Forty-seven poststroke hemiparetic patients were hospitalized to receive 12 sessions of 40-min low-frequency repetitive transcranial magnetic stimulation over the nonlesional hemisphere and daily occupational therapy for 15 days. Motor function was evaluated with the Fugl-Meyer Assessment and Wolf Motor Function Test. The functional magnetic resonance imaging with motor tasks was performed at admission and discharge. The laterality index of activated voxel number in Brodmann areas 4 and 6 on functional magnetic resonance imaging was calculated (laterality index range of -1 to +1). Patients were divided into two groups based on functional magnetic resonance imaging findings before the intervention: group 1: patients who showed bilateral activation (n = 27); group 2: patients with unilateral activation (n = 20).

RESULTS

Treatment resulted in improvement in Fugl-Meyer Assessment and Wolf Motor Function Test in the two groups (P < 0·01). The treatment also resulted in a significant increase in laterality index in group 1 (P < 0·05), suggesting a shift in activated voxels to the lesional hemisphere. Patients of group 2 showed a significant increase in lesional hemisphere activation (P < 0·05).

CONCLUSIONS

The results of serial functional magnetic resonance imaging indicated that our proposed treatment can induce functional cortical reorganization, leading to motor functional recovery of the affected upper limb. Especially, it seems that neural activation in the lesional hemisphere plays an important role in such recovery in poststroke hemiparetic patients.

Ipsilateral motor pathways after stroke: implications for non-invasive brain stimulation

In humans the two cerebral hemispheres have essential roles in controlling the upper limb. The purpose of this article is to draw attention to the potential importance of ipsilateral descending pathways for functional recovery after stroke, and the use of non-invasive brain stimulation (NBS) protocols of the contralesional primary motor cortex (M1). Conventionally NBS is used to suppress contralesional M1, and to attenuate transcallosal inhibition onto the ipsilesional M1. There has been little consideration of the fact that contralesional M1 suppression may also reduce excitability of ipsilateral descending pathways that may be important for paretic upper limb control for some patients. One such ipsilateral pathway is the cortico-reticulo-propriospinal pathway (CRPP). In this review we outline a neurophysiological model to explain how contralesional M1 may gain control of the paretic arm via the CRPP. We conclude that the relative importance of the CRPP for motor control in individual patients must be considered before using NBS to suppress contralesional M1. Neurophysiological, neuroimaging, and clinical assessments can assist this decision making and facilitate the translation of NBS into the clinical setting.

Single session of dual-tDCS transiently improves precision grip and dexterity of the paretic hand after stroke

BACKGROUND

After stroke, deregulated interhemispheric interactions influence residual paretic hand function. Anodal or cathodal transcranial direct current stimulation (tDCS) can rebalance these abnormal interhemispheric interactions and improve motor function.

OBJECTIVE

We explored whether dual-hemisphere tDCS (dual-tDCS) in participants with chronic stroke can improve fine hand motor function in 2 important aspects: precision grip and dexterity.

METHODS

In all, 19 chronic hemiparetic individuals with mild to moderate impairment participated in a double-blind, randomized trial. During 2 separate cross-over sessions (real/sham), they performed 10 precision grip movements with a manipulandum and the Purdue Pegboard Test (PPT) before, during, immediately after, and 20 minutes after dual-tDCS applied simultaneously over the ipsilesional (anodal) and contralateral (cathodal) primary motor cortices.

RESULTS

The precision grip performed with the paretic hand improved significantly 20 minutes after dual-tDCS, with reduction of the grip force/load force ratio by 7% and in the preloading phase duration by 18% when compared with sham. The dexterity of the paretic hand started improving during dual-tDCS and culminated 20 minutes after the end of dual-tDCS (PPT score +38% vs +5% after sham). The maximal improvements in precision grip and dexterity were observed 20 minutes after dual-tDCS. These improvements correlated negatively with residual hand function quantified with ABILHAND.

CONCLUSIONS

One bout of dual-tDCS improved the motor control of precision grip and digital dexterity beyond the time of stimulation. These results suggest that dual-tDCS should be tested in longer protocols for neurorehabilitation and with moderate to severely impaired patients. The precise timing of stimulation after stroke onset and associated training should be defined.

Neuromodulation for brain disorders: challenges and opportunities

The field of neuromodulation encompasses a wide spectrum of interventional technologies that modify pathological activity within the nervous system to achieve a therapeutic effect. Therapies including deep brain stimulation, intracranial cortical stimulation, transcranial direct current stimulation, and transcranial magnetic stimulation have all shown promising results across a range of neurological and neuropsychiatric disorders. While the mechanisms of therapeutic action are invariably different among these approaches, there are several fundamental neuroengineering challenges that are commonly applicable to improving neuromodulation efficacy. This paper reviews the state-of-the-art of neuromodulation for brain disorders and discusses the challenges and opportunities available for clinicians and researchers interested in advancing neuromodulation therapies.

Brain-derived neurotrophic factor--a major player in stimulation-induced homeostatic metaplasticity of human motor cortex?

Repetitive transcranial magnetic stimulation (rTMS) of the human motor hand area (M1_HAND) can induce lasting changes in corticospinal excitability as indexed by a change in amplitude of the motor-evoked potential. The plasticity-inducing effects of rTMS in M1_HAND show substantial inter-individual variability which has been partially attributed to the val⁶⁶met polymorphism in the brain-derived neurotrophic factor (BDNF) gene. Here we used theta burst stimulation (TBS) to examine whether the BDNF val⁶⁶met genotype can be used to predict the expression of TBS-induced homeostatic metaplasticity in human M1_HAND. TBS is a patterned rTMS protocol with intermittent TBS (iTBS) usually inducing a lasting increase and continuous TBS (cTBS) a lasting decrease in corticospinal excitability. In three separate sessions, healthy val⁶⁶met (n = 12) and val⁶⁶val (n = 17) carriers received neuronavigated cTBS followed by cTBS (n = 27), cTBS followed by iTBS (n = 29), and iTBS followed by iTBS (n = 28). Participants and examiner were blinded to the genotype at the time of examination. As expected, the first TBS intervention induced a decrease (cTBS) and increase (iTBS) in corticospinal excitability, respectively, at the same time priming the after effects caused by the second TBS intervention in a homeostatic fashion. Critically, val⁶⁶met carriers and val⁶⁶val carriers showed very similar response patterns to cTBS and iTBS regardless of the order of TBS interventions. Since none of the observed TBS effects was modulated by the BDNF val⁶⁶met polymorphism, our results do not support the notion that the BDNF val⁶⁶met genotype is a major player with regard to TBS-induced plasticity and metaplasticity in the human M1_HAND.

Modeling developmental plasticity after perinatal stroke: defining central therapeutic targets in cerebral palsy

Perinatal stroke is presented as the ideal human model of developmental neuroplasticity. The precise timing, mechanisms, and locations of specific perinatal stroke diseases provide common examples of well defined, focal, perinatal brain injuries. Motor disability (hemiparetic cerebral palsy) constitutes the primary adverse outcome and the focus of models explaining how motor systems develop in health and after early injury. Combining basic science animal work with human applied technology (functional magnetic resonance imaging, diffusion tensor imaging, and transcranial magnetic stimulation), a model of plastic motor development after perinatal stroke is presented. Potential central therapeutic targets are revealed. The means to measure and modulate these targets, including evidence-based rehabilitation therapies and noninvasive brain stimulation, are suggested. Implications for clinical trials and future directions are discussed.

A review of evidence linking disrupted neural plasticity to schizophrenia

The adaptations resulting from neural plasticity lead to changes in cognition and behaviour, which are strengthened through repeated exposure to the novel environment or stimulus. Learning and memory have been hypothesized to occur through modifications of the strength of neural circuits, particularly in the hippocampus and cortex. Cognitive deficits, specifically in executive functioning and negative symptoms, may be a corollary to deficits in neural plasticity. Moreover, the main excitatory and inhibitory neurotransmitters associated with neural plasticity have also been extensively investigated for their role in the cognitive deficits associated with schizophrenia. Transcranial magnetic stimulation (TMS) represents some of the most promising approaches to directly explore the physiological manifestations of neural plasticity in the human brain. Three TMS paradigms (use-dependent plasticity, paired associative stimulation, and repetitive TMS) have been used to evaluate neurophysiological measures of neural plasticity in the healthy brain and in patients with schizophrenia, and to examine the brain's responses to such stimulation. In schizophrenia, deficits in neural plasticity have been consistently shown which parallel the molecular evidence appearing to be entwined with this debilitating disorder. Such pathophysiology may underlie the learning and memory deficits that are key symptoms of this disorder and may even be a key mechanism involved in treatment with antipsychotics.

The dynamic nature of top-down signals originating from prefrontal cortex: a combined fMRI-TMS study

The prefrontal cortex (PFC) is proposed to be the source of top-down signals that can modulate extrastriate visual processing in accordance with behavioral goals, yet little direct causal evidence for this hypothesis exists. Using theta burst transcranial magnetic stimulation, we disrupted PFC function in human participants before performing a working memory task during fMRI scanning. PFC disruption decreased the tuning of extrastriate cortex responses, coinciding with decrements in working memory performance. We also found that activity in the homologous PFC region in the nonstimulated hemisphere predicted performance following disruption. Specifically, those participants with greater homologous PFC activity and greater connectivity between this region and extrastriate cortex were the most resistant to PFC disruption. These findings provide evidence for a compensatory mechanism following insults to the brain, and insight into the dynamic nature of top-down signals originating from the PFC.

Noninvasive brain stimulation in neurorehabilitation

Stroke is the major cause of long-term disability worldwide, with impaired manual dexterity being a common feature. In the past few years, noninvasive brain stimulation (NIBS) techniques, such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), have been investigated as adjuvant strategies to neurorehabilitative interventions. These NIBS techniques can be used to modulate cortical excitability during and for several minutes after the end of the stimulation period. Depending on the stimulation parameters, cortical excitability can be reduced (inhibition) or enhanced (facilitation). Differential modulation of cortical excitability in the affected and unaffected hemisphere of patients with stroke may induce plastic changes within neural networks active during functional recovery. The aims of this chapter are to describe results from these proof-of-principle trials and discuss possible putative mechanisms underlying such effects. Neurophysiological and neuroimaging changes induced by application of NIBS are reviewed briefly.

NON-INVASIVE BRAIN STIMULATION IN CHILDREN: APPLICATIONS AND FUTURE DIRECTIONS

Transcranial magnetic stimulation (TMS) is a neurostimulation and neuromodulation technique that has provided over two decades of data in focal, non-invasive brain stimulation based on the principles of electromagnetic induction. Its minimal risk, excellent tolerability and increasingly sophisticated ability to interrogate neurophysiology and plasticity make it an enviable technology for use in pediatric research with future extension into therapeutic trials. While adult trials show promise in using TMS as a novel, non-invasive, non-pharmacologic diagnostic and therapeutic tool in a variety of nervous system disorders, its use in children is only just emerging. TMS represents an exciting advancement to better understand and improve outcomes from disorders of the developing brain.

Seven capital devices for the future of stroke rehabilitation

Stroke is the leading cause of long-term disability for adults in industrialized societies. Rehabilitation's efforts are tended to avoid long-term impairments, but, actually, the rehabilitative outcomes are still poor. Novel tools based on new technologies have been developed to improve the motor recovery. In this paper, we have taken into account seven promising technologies that can improve rehabilitation of patients with stroke in the early future: (1) robotic devices for lower and upper limb recovery, (2) brain computer interfaces, (3) noninvasive brain stimulators, (4) neuroprostheses, (5) wearable devices for quantitative human movement analysis, (6) virtual reality, and (7) tablet-pc used for neurorehabilitation.

New modalities of brain stimulation for stroke rehabilitation

Stroke is a leading cause of disability, and the number of stroke survivors continues to rise. Traditional neurorehabilitation strategies aimed at restoring function to weakened limbs provide only modest benefit. New brain stimulation techniques designed to augment traditional neurorehabilitation hold promise for reducing the burden of stroke-related disability. Investigators discovered that repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS), and epidural cortical stimulation (ECS) can enhance neural plasticity in the motor cortex post-stroke. Improved outcomes may be obtained with activity-dependent stimulation, in which brain stimulation is contingent on neural or muscular activity during normal behavior. We review the evidence for improved motor function in stroke patients treated with rTMS, tDCS, and ECS and discuss the mediating physiological mechanisms. We compare these techniques to activity-dependent stimulation, discuss the advantages of this newer strategy for stroke rehabilitation, and suggest future applications for activity-dependent brain stimulation.